6

2. REVIEW OF LITERATURE

The members of the family Nemipteridae commonly known as

threadfin breams, whiptail breams, monocle breams, dwarf monocle and

coral breams constitute about 64 species. They inhabit in the shallow

coral reef to deeper shelf areas living in the demersal regions ranging from

sandy to muddy bottoms. These fishes may remain solitary or form schools

in the sea and exhibit no territorial preference (Russell, 1990a).

The available literatures suggest that most of the studies on

nemipterids are limited to the commonly occurring species. The

distribution of the nemipterids is patchy, with the exception of Nemipterus

japonicus, N. zysron, Parascolopsis eriomma and Scolopsis vosmeri.

Therefore, the biological information is also patchy, and most of the works

are from southeast Asian countries bordering west pacific region.

Most of the works on nemipterids from our coasts are on their

taxonomy, distribution and utilisation using advanced processing

technology. Though some biological studies have been carried out on the

threadfin breams like N. japonicus, N. mesoprion, N. delagoae, N. tolu and

N. peronii, most of them are confined to the species from the east coast,

south west coast and north west coast. Thus the information is patchy

with gaps especially with respect to the population from the central west

coast. Moreover, in some cases the very validity of their identification is

7

doubtful due to the in-built uncertainties and fluidity in taxonomic

characters adopted for the group.

2.1. Taxonomy

The members of the family Nemipteridae are all marine belonging to

order Perciformes. They belong to super family Sparoidea, which includes

other families like Sparidae (porgies), Lethrinidae (emperor fishes) and

Centracanthidae (picarels). Akazaki (1962) and Johnson (1980) have

discussed relationship of the sparoid fishes. Johnson (op.cit.) is of the

opinion that nemipertids are more closely related to lethrinids than any

other sparoides. Some of the recent works (Jordan, 1923; Berg, 1940;

Gosline, 1971; Lindbergh, 1971; Greenwood et al., 1974; Nelson, 1984 and

1994) have reduced the variations in the general classification of the fishes.

In the most commonly followed classification, the threadfin breams belong

to Super Class: Teleostomi; Class: Osteichthyes; Sub Class: Actinoptrygii;

Order: Perciformes; Sub Order: Percoidei; Super Family: Sparoidea; Family:

Nemipteridae. The generic name Nemipterus was given by Swainson (1839),

while GUnther (1859) gave the name Synagris.

Threadfin breams in Indian waters were first documented by Day

(1875-77) under genus Synagris GUnther (family: Percidae), which were

earlier placed under a different genus Dentex Cuvier and Valenciennes.

Munro (1955) recorded only 4 species from the Gulf of Mannar and Sri

8

Lanka and placed them under family Nemipteridae of Suborder Percoidei

and order Perciformes. Talwar and Kacker (1984) listed 8 species of Genus

Nemipterus and 17 species of Genus Scolopsis under the family

Nemipteridae.

Nelson (1994) described 62 species of nemipterids under four Genera

Viz. Nemipterus (Swainson), Scolopsis (Cuvier) Parascolopsis (Cuvier)

Pentapodus (Quay and Gaimard) and Scaevius (Whitley). Pentapodus was

placed under nemipterids following Johnson (1975, 1980), though formerly

it was isolated in a separate family Pentapodidae. Weber and Beaufort

(1936) placed all the species occurring in Indo- Australian Archipelago

under sub-family Nemiptirinae. They included Genera 1) Scolopsis Cuvier,

2) Gnathodentex Bleeker, 3) Monotaxis Bennett 4) Nemipterus Swainson, 5)

Pentapus Cuvier and Valenciennes, 6) Gymnocranius Klunzinger and 7)

Symphorus GUnther. Under Genus Scolopsis they described 16 species and

under Genus Nemipterus 20 species.

Taxonomy

Nemipterids are considered to be one of the taxonomically difficult

groups. Fowler (1904, 1931, 1933 and 1943), Weber and Beaufort (1936)

and Akazaki (1959 and 1962) previously reviewed taxonomic status of

these fishes. Nevertheless, the confusion continues. Fowler (1972) has

reported 7 species under genus Nemipterus from the Chinese waters. The

9

reviews of Nemipterus species of Thailand (Wongratana, 1972, 1974),

Taiwan (Lee, 1986) and western Indian Ocean (Russell, 1986) have

attempted to solve some of the taxonomic problems. In spite of these

efforts, identification and systematics of these fishes is full of confusion.

Many species of nemipterids are similar in morphology, hence colour

differences separate the taxa (Eggleston, 1973) making the identification of

preserved specimen difficult. The descriptions of species under family

Nemipteridae were revised to reduce the confusion in identification, and the

work is still in progress. Hence, the FAO species catalogue for the

nemipterid species of the world (Russell, 1990a) which is a product of on

going revision of the family Nemipteridae is not complete (Russell personal

communication).

Russell (1991a) described a new species N. thosaporni previously

identified as N. marginatus. In addition, he re-described N. marginatus

(Val.), N. mesoprion (Bleeker) and N. nematopus (Bleeker) from west pacific

region and Southern Japan to Indonesia. Russell (1991b) established the

validity of N. furcosus (val.) which was hitherto wrongly identified as N.

perond (Val.) and re-described as a senior Synonym of N. tolu (Val.).

The nemipterids from Indian waters so far recorded are placed under

genera Nemipterus (Swainson), Scolopsis (Cuvier), and Parascolopsis

10

(Boulenger). The species of these genera recorded from Indian waters are

given below.

Species of the genus Nemipterus recorded from Indian waters.

1. Nemipterus japonicus (Bloch, 1791); Spars japonicus Bloch, 1791,

Naturges. Ausland. Fisches., 5: 110.

Synonyms: Dentex blochii Bleeker (1851c); Synagris japonicus Day

1875-77 in Day (1889); Nemipterus japonicus (Bloch) in Talwar and

Kacker (1984)

2. Nemipterus bipunctatus (Ehrenberg, 1830); Dentex bipunctatus

Ehrenberg in C. &V., 1830b. Hist. Nat. poiss.,6: 247 (Dejedda, Red

Sea)

Synonyms: Synagris bleekeri (Day, 1875 - 77) in Day (1889);

Nemipterus mulloides Smith (1939)(Preoccupied); Nemipterus

delagoae Smith (1941); N. delagoae in Fisher and Bianchi (1984)

Nemipterus bleekeri (Day, 1875-77) in Talwar and Kacker (1984);

mostly reported as N. bleekeri in Indian waters. Reported as N.

delagoae (Smith) of Quillon, south west coast of India by Rajagopalan

et al., (1975), from Waltair by Rao & Rao (1981b) and along Cochin

waters by John and Hameed (1983).

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3. Nemipterus marginatus (Valenciennes, 1830) Dentex marginatus

Valenciennes in C. &V., 1830b., Hist. Nat. poiss.,6: 245 ( Vanicolo;

Java) .

Reported first time in India by Shameem and Rao (1997) as

Nemipterus marginatus (Valenciennes, 1830)

4. Nemipterus nematophorus (Bleeker, 1853) Nemipterus nematophorus

(Bleeker, 1853, Nat. Ti'dschr. Ned.-Indie 5: 500 (Padang, Sumatra).

Synonyms: Dentex filamentosus Valenciennes in C. and V. 1830b,

Synagris macronemus Gunther (1859), Cantharus filamentosus

Ruppell. Reported as N. luteus (Schneider, 1801) in Talwar and

Kacker (1984). Murty (1977) however considered N. luteus Schneider

as a valid name. The priority status of Synonym is not yet clear.

5. Nemipterus peronii (Valenciennes, 1830). Dentex peronii Valenciennes, in

C.V., 1830b, Hist. nat. poiss., 6:245,p1.154 (no type locality).

Synonyms: - Dentex tolu Valenciennes in C. and V. (1830b); Synagris

tolu (Day, 1875); Dentex Mulloides Bleeker (1852); reported as

Nemipterus tolu Valenciennes in Taiwar and Kacker (1984). N.

peronii, (Valenciennes, 1830) was reported from Tuticorin waters (Rao

& Rao, 1986a) and along Cochin waters John and Hameed (1983).

12

6. Nemipterus zysron (Bleeker, 1856-57): Dentex zysron Bleeker, 1857, Nat.

Ti'dschr. Ned. - Indie. 12: 219 (Nias).

Synonyms: Dentex metopias Bleeker (1857). Mostly reported as N.

metopias Fisher and Whitehead (1974) Fisher and Bianchi (1984) but

N. zysron has priority (Russell, 1990a). Along Indian coast, Indira

(1981), Madanmohan and Gopakumar (1981) reported occurrence of

N. metopias.

7. Nemipterus randalli Russell (1986): Nemipterus randalli Russell, 1986,

Senckenberg. Biol. 67: 23, fig. 2 (Persian Gulf; Red Sea; Gulf of Aden;

Zanzibar; Seychelles; Madagascar; Pakistan; India). This species was

described by Russell while reviewing the Nemipterid fishes of the

world. There is no general agreement on this description. According

to him the fishes hitherto recorded as N. mesoprion (Bleeker, 1853) in

Indian waters are wrongly identified so. Mishra and Krishnan (1992)

have recorded N. randalli from Andaman waters.

8. Nemipterus mesoprion (Bleeker, 1853): Dentex mesoprion Bleeker, 1853a,

Nat. Ti'dschr. Ned. -Indie , 4: 255 (Priaman, Sumatra). Nemipterus

mesoprion: Weber and Beauport, 1936. The species does not have a

caudal filament (Russell, 1990a, 1991a). However, Indian workers

have been recording N. mesoprion following the description given with

the first report of the species by Murthy (1978). But, according to

13

Russell (1986) the species occurring in west cost of India is

Nemipterus randalli.

9. Nemipterus hexodon (Quay & Gaimard, 1824): Dentex hexodon Quoy &

Gaimard, 1824, Voy. "Uranie", Zool.,: 301 (Timor). Synonyms:

Dentex (Synagris) notatus Day (1870); Reported as Nemipterus

hexodon (Quay & Gaimard, 1824) in Talwar and Kacker (1984).

10. Nemipterus furcosus (Valenciennes, 1830) a valid Species (Russell,

1991b) may be occurring in Indian waters if wrongly identified as N.

peronii,) Dentex furcosus Valenciennes in C. and V. 1830b Hist. Nat.

poiss., 6: 245, (Trincomalee Srilanka) p1.154. Synonyms: Dentex

upeneoides Bleeker (1852c). Reported along Sri Lankan waters by

Munro (1955).

Species of the genus Parascolopsis recorded from Indian waters

1. Parascolopsis aspinosa (Rao & Rao, 1981); Scolopsis aspinosa Rao and

Rao, 1981, Proc. Kon. Ned. Akad. Wetensch., Ser. C, 84:134, Fig.1,3

(Waltair, India). Synonym: Parascolopsis jonesi Talwar (1986).

2. Parascolopsis boesemani (Rao & Rao, 1981); Scolopsis boesemani Rao &

Rao, 1981, Proc. Kon. Ned. Akad. Wetensch., Ser. C, 84: 139, fig.2, 4

(Waltair, India).

14

3. Parascolopsis townsendi (Boulenger, 1901): Parascolopsis townsendi

Boulenger, 1901, Ann. Mag. Nat. Hist.,(7) 7: 262, pl. 6(Gulf of Oman).

4. Parascolopsis inermis (Schlegel, 1843): Scolopsis inermis Schlegel in

Temminck & Schlegel, 1843, Fauna Japonica: 63, pl. 28, fig.1

(Japan). Talwar and Kacker (1984) are of the opinion that the

distribution of the species is doubtful.

The taxonomic status of the members of genus Scolopsis Cuvier

(1815) occurring in Indian waters was first dealt by Rao and Rao (1981a)

who placed them under Scolopsis Cuvier, 1815, which included the species

of Parascolopsis also.

Species of the genus Scolopsis recorded from Indian waters

1. Scolopsis vosmeri (Bloch, 1792); Anthias vosmeri Bloch, 1792, Naturges.

Ausland. Fische 6:120, pl. 321 (Japan Sea). Synonyms: Anthias

japonicas Bloch (1793).

2. Scolopsis ciliatus (Lacepede, 1802): Holocentrus ciliatus Lacdpede, 1802,

Hist. nat. poiss., 4: 333 (no locality given) ; Scolopsis ciliatus (Day,

1889) from Port Blair Andaman.

Representatives of Genus Pentapodus (Quoy and Gaimard, 1824) are

mostly found in the West Pacific region (Russell, 1990a), their distribution

in Indian waters is yet to be recorded.

15

The genus Scaeuius Whitley, 1947 is represented by a single species

Scaevius milli (Bory de Saint- Vincent, 1823) in the northwestern

Australian waters; and is not known from Indian waters.

2.2. Length-weight relationship and relative condition factor

The length-weight relationships of different species of nemipterids

from waters around India and other parts of the world are available. In

Indian waters, Krishnamoorthi (1971) observed that a single equation was

not possible as there was significant difference in the regression equations

of males and females of N. japonicus. He gave the equation for males as W

= 0.001752 L 2.0769 and for females, W = 0.0000183 L 2 ' 9423 . Vinci and Nair

(1974) gave common length-weight relationship of N. japonicus along Kerala

coast as log W = -5.4793 + 2.8487 log L. They also suggested that the

regression equation of both sexes of the species of Kerala, differed from that

of Andhra and Orissa due to difference in stock.

The length-weight relationship of N. mesoprion of Kakinada region

was worked out by Murty (1981) in the form of a common equation, log W =

-4.650901 + 2.877071 log L. Murty (1984) observed that difference of the

regression coefficients between sexes in the case of N. japonicus of

Kakinada region was significant. He derived the equation for male, log W =

- 3.65045 + 2.43025 log L and for female, log W = - 4.78137 + 2.95688 log

L. In fishes with lengths lesser than 155 mm, the K2, value for males was

16

always higher than that for females. For N. mesoprion in Chennai region

the length-weight equation for males was log W = -4.7926 + 2.9692 log L

and for females was log W = 3.0602 + 2.1570 log L which differed

significantly (Vivekanandan and James, 1984). Acharya and Dwivedi

(1980-81) have worked out the length-weight relationship of N. japonicus

from the Bombay region as log W = -4.4516 + 2.8069 log L for males and

log W = -5.0034 + 3.0634 log L for females. In N. japonicus from the trawl

of grounds of Chennai the length-weight relationship among males and

females did not differ significantly. The pooled equation was log W = -

4.8665 + 2.9661 log L (Vivekanandan and James, 1984).

Lee (1973) gave length-weight equation for N. japonicus from Hong

Kong region as W = 0.0176 L3 .°246 for males and W = 0.0147 L3.°939 for

females. Hoda (1976) found that among the N. japonicus of Pakistan coast

the length-weight relationship between sexes did not differ significantly and

proposed a combined equation, log W = -6.875413 + 3.090598 log L. He

also computed the condition 'K' for both the sexes. Gopal and

Vivekanandan (1991) have reported that the length-weight relationship

between sexes of N. japonicus of Veraval region did not differ significantly.

The combined equation proposed by them was log W = -4.2570 + 2.7488

log L. Along the Kochi region (John and Hameed, 1994) the length-weight

relationship for N. japonicus was log W = - 4.3794 + 2.7831 log L and that

17

for females was log W = - 4.8315 + 2.9881 log L. The regression equation

for males of N. mesoprion was log W = - 4.4430 + 2.7983 log L and for

females was log W = - 4.6385 + 2.8873 log L. For both the species, the

exponent value '13' for males and females was less than 3. The regression

equations between sexes differed significantly among N. japonicus but

among N. mesoprion, difference was not significant. Hence they proposed a

combined equation log W = - 4.5641 + 2.8163 log L for N. mesoprion. Raje

(1996) found that there was no significant difference in length-weight

relation between males and females of N. mesoprion from Veraval region.

Therefore the combined equation was log W = -10.7134 + 2.9124 log L. He

also reported that the peak condition of females was up to March and that

for males upto April. Length-weight relation for N. japonicus along Kuwait

waters (Samuel, 1990) was log W = 0.02448 + 2.78952 log L for males and

log W = 0.01123 + 3.0399 log L for females. The K. value had 3 peaks

suggesting two spawning periods.

Madanmohan and Velayudhan (1984) observed that in the case of N.

delagoae from Vizhinjam Kerala, the equation for males was

log W = -4.894391+ 2.969385 log L and for females, log W = -

4.675841+2.881551 log L. The difference between the regression equations

for males and females was not significant. Therefore the combined

equation derived by them was log W = -4.891125 +2.972582 log L.

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2.3. Food and feeding

Most of the earlier studies on the food and feeding habits of

nemipterids were of generalized/gross nature and did not provide details.

In the first ever report (Anon, 1960) the most common food items of N.

japonicus obtained from the southern part of the Indian coast were

recorded as prawns, polychaetes and small fish. Food habits of N.

japonicus from trawl catches along Mangalore shore did not differ between

seasons (Kuthalingam, 1965), but differed among those caught from

different depths. The food of the fish from 10-20 m depth mainly consisted

of Metapenaeus dobsonii and Parapaenopsis stylifera along with

polychaetes, foraminiferans, and fishes. Among them the prawn M.

dobsonii (35%) dominated. In slightly deeper waters of 20-30 m depth,

Parapaenopsis stylifera formed the bulk (40%) of the food. At 30-40 m

depth, besides crustaceans teleosts were included in the diet while at 40-

50 m, cannibalism was observed. George et al. (1968) reported that N.

japonicus off Kochi consumed crustaceans, predominantly amphipods.

They were considered to be active predators possibly by sight

(Krishnamoorthi, 1971), feeding substantially on crustaceans, mulluscs,

annelids and echinoderms. N. japonicus from shallow waters were reported

to feed on mostly prawns and those from deeper waters on fish and crabs

(Vivekanandan, 1990). Squilla, crab prawns, teleosts, cephalopods,

19

amphipods, polychaetes, were encountered in the order dominance in the

gut of N. japonicus caught off Visakhapatnam (Rao and Rao, 1991). Their

feeding intensity was recorded to be the highest between March to

November and lowest during December and February. Off Bombay coast

(Acharya et al., 1994) also the N. japonicus were found to feed on bottom

mainly on crustaceans, fishes polychaetes and salps.

Rao (1989) observed that the food of N. mesoprion from the Andhra

coast was mainly crustaceans such as young prawns, crabs and squilla

and so also teleosts. Along Gujarat coast, N. mesoprion was found to feed

on crustaceans, fishes, molluscs and annelids in the order of preference

(Raje, 1996).

The N. delagoae off Tutukkudi fed predominately on fishes, prawns

and crabs (Hamsa et al., 1994). They also fed on brittle star, cuttle fishes,

gastropods, bivalves, squilla, polychaetes, alphids, isopods and

amphipodes.. N. delagoae (Smith) from Vizinjam (Madanmohan and

Velayudhan, 1984) consumed crustaceans (74.5%) mainly prawns, crabs

and Squilla. They also fed on fishes such as Stolephorus sp., Saurida,

Trichiurus sp., Platycephalus sp., Thryssa and molluscs, such as Octopus,

Sepia and mussels.

N. bathybius, N. japonicus, N. virgatus from Hong Kong waters

(Eggleston, 1972) were reported to be active predators feeding during day

20

time and hunting by sight. Adults among them fed mainly on crustaceans,

fishes and cephalopods. Range of food items narrowed down as they grew

and the prey size increased. Cephalopods crustaceans, polychaetes and

lamellibranchs formed the bulk of the diet of N. virgatus, N. bathybius and

N. japonicus respectively. The Nemipterus tolu of the South China Sea was

an active carnivore, day light feeder, feeding on fishes, crustaceans,

mollucs and polychaetes. Stomach contents of bigger fish varied less than

that of smaller fish (Said et al., 1983). N. japonicus of Daya Bay, China fed

mainly on benthos and small zooplankton (Zhuang, 1990). Feeding of N.

peronii, along northwest Australia was observed to be during day

(Sainsbury and Whitelaw, 1984). N. furcosus from gulf of Carpentaria ,

Australia showed seasonal differences in food habits (Salini et al. 1994). In

a related species N. nemurus from South-China Sea, crustaceans

dominated the food composition (Daud and Taha, 1986).

2.4 Reproduction

The first ever report on the reproduction of nemipterids from Indian

waters was on that of N. japonicus (Anon, 1960). They were reported to

begin to attain maturity from September and move to deeper waters beyond

50m along Mangalore coast after attainment of sexual maturity

(Kuthalingam, 1965). He also suggested that breeding took place during

January or February. According to Krishnamoorthi (1971), N. japonicus

21

along the east coast spawns for the first time on attainment of 160 to 179

mm total length, and second time on attainment of 222 mm total length.

In N. japonicus additional growth of upper region of caudal fin in males,

nearly one and half time more than that of females was treated as

secondary sexual character (Nammaiwar, 1973). Along the east coast, N.

japonicus was found to breed twice a year - December - February and June

- July, and the fishes ranging in total length from 132 to 209 mm had a

fecundity of 10.5 to 80.8 thousand (Dan, 1977). Along Kakinada, N.

japonicus was observed to be a fractional spawner releasing the ova in two

batches during the protracted spawning season extending from August to

April. The species at Kakinada attained first maturity when they were 125

mm long and had a fecundity of 23,094 to 1,39,160 while in the size range

of 134 to 199 mm (Murty, 1984). Off Mumbai, N. japonicus spawned from

August to November with a peak during October (Acharya and Dwivedi,

1980-81). The occurrence of low catch of running N. japonicus along

Kuwait in deeper waters through out the year (Samuel, 1986) suggests that

they also move to deeper waters for breeding as observed along Mangalore

coast. Gonadal maturation in N. japonicus off Visakhapatnam (Rao and

Rao, 1991) is between August and October. Further, N. japonicus with ripe

ovaries were observed offthe coast of Visakhapatnam from January to April,

wherein the males outnumbered the females. Along Madras coast

22

(Vivekanandan and James, 1986) N. japonicus matured at 145 mm total

length and had an extended spawning period from June to March with a

peak between December to March. Acharya (1990) recorded July to

December as the breeding season off Mumbai coast with a peak during

November to December. Vivekanandan (1990) observed that mature

females of N. japonicus were in a larger number in deeper waters of Tamil

Nadu and South Andhra Pradesh.

N. mesoprion were found to attain sexual maturity when 100 mm

long, and were recorded to be fractional spawners releasing ova in two

batches during a single spawning season extending from December to April

(Murty, 1981). The males outnumbered the females in N. mesoprion landed

at Visakhapatnam (Rao, 1989). Along Veraval, the sex ratio for N.

mesoprion was 2.57:1 (Raje, 1996). The females of the fishes attained first

maturity at 134 mm and the fecundity ranged from 50,344 to 64,369 in

fishes of size ranging from 104 to 198 mm. They are also known to spawn

from September to March with a first peak in September and second peak

in November-December.

Sex ratio, maturity and spawning season for N. delagoae off Mumbai

were recorded by Muthiah and Pillai (1979). The females achieved first

maturity when they were 135 mm long. The sex ratio was 1:1.01 and the

fecundity ranged from 5,578 to 93,948 with a high correlation with length,

23

body weight and weight of gonad. Along Vizhinjam these fishes spawned

twice a year with a peak during September to June (Madanmohan and

Velayudhan, 1986). The size at first maturity was between 164 to 170 mm,

and the annual fecundity ranged from 86,184 to 4,97,230, which increased

with increase in both length as well as weight.

The histological examinations of gonads of Scolopsis monogramma, S.

taeniopterus, S. bilineatus exhibited protogynus hermaphroditism (Young

and Martin, 1985). In N. peronii and Pentapodus porous, the evidence

suggested the occurrence of hermaphroditism. They observed that the size

related skewness in S. monogramma, S. taeniopterus and S. bilineatus was a

result of protogynus hermaphroditism and not sexually differentiated

growth rates. N. peronii of northwest shelf of Australia was found to have

ripe eggs throughout the year, the proportion of ripe eggs was highest in

November and December (Sainsbury and Whitelaw, 1984). The N. tolu from

the trawl grounds of the South China Sea was found to have two prolonged

spawning periods one from November to February and another starting

from May/June (Said et al., 1983). Along Hong Kong waters, Eggleston

(1972) studied the spawning habits of three species N. japonicus, N.

virgatus and N. bathybius. Spawning of N. virgatus was around the islands

in the northern part of South China Sea (Zhang and Lee, 1980). While

surveying the ichthyoplanktons of Daya Bay, China, Wang (1990) observed

24

a large number of eggs of N. virgatus and N. japonicus, abundance of which

decreased during summer. He also carried out studies on the hatching and

larval development of these fishes. In the northern part of south China sea,

spawning season of N. virgatus was observed to be from April to June

(Zhang, 1986).

2.5 Age, growth, stock and population dynamics

Age and growth details of fish form an important input for stock

assessment studies. In the earliest recorded work on growth, the Japanese

threadfin bream N. japonicus had the modal size of 120 - 130 mm in

September-December which advanced to 140 mm by January- March

(Anon, 1960). Along South Sea coast, Israel (Ben -Tuvia, 1968) N.

japonicus measuring up to 130 mm were of '0'-year class and those

measuring 170 mm were of one-year class.

In N. virgatus of the South China Sea, males grew faster than females

(Eggleston, 1970) resulting in size difference between them. At

Visakhapatnam, N. japonicus is reported to grow to an average size of 150

mm, 210 mm, 240 mm at the end of 1st, 2nd and 3rd years respectively

(Krishnamoorthi, 1971). Eggleston (1972) suggested that growth curves for

males and females of Nemipterids should be plotted separately as the

growth rate of male and females of N. Virgatus, N. bathybius and N.

japonicus differed. Males and females of N. japonicus caught by Hong Kong

25

vessels were found to have maximum length of 311 mm and 357 mm and

maximum age of 7 and 8 years respectively (Lee, 1973). Krishnamoorthi

(1974) observed size differences between the sexes of N. japonicus along

Visakhapatnam, the females being generally smaller. Krishnamoorthi

(1976) worked out yield per recruit in weight (Y w/R) and in number (Y. /R)

for the stocks of N. japonicus off Andhra Pradesh coast and opined that the

stocks were under exploited, as the rate of exploitation (E') was only 0.3.

In N. vigratus off Persian Gulf and Arabian Sea the formation of growth

check was once a year which is considered to be associated with spawning

(Nekrasov, 1979). Age determination using the otolith of N. virgatus was

carried out by Kao and Liu (1979), wherein a single growth check was

noticed by May in the population from South China Sea and by June in

that from East China Sea. They observed that males grew faster. The

parameters of von- Bertalanffy's growth formula (VBGF) in East China Sea

were 31.26 cm, K = 0.3216, to = -0.8998 for females and L.= 41.37 cm

K = 0.3026, to = -0.2663 for males. For fishes in South China Sea, females

had L.= 27.98 cm, K = 0.4404, t o = -0.8135 and males had, I.= 34.18 cm,

K = 0.4474, to= -0.2016.

In Indian waters, Acharya and Dwivedi (1980-81) observed difference

in the growth rates among males and females of N. japonicus along Mumbai

coast. They further observed that N. japonicus on an average grows at the

26

rate of 12.91 mm per month and attains a size of 155 mm in the first year

and later, grows at a rate of 5 mm per month and attains a size of 211.5

mm in the second year. N. Japonicus attained a length 136 mm, 186 mm

and 230 mm by the end of 1st, 2nd and 3rd year respectively along the

Kerala coast (Vinci, 1982). N. mesoprion along Kakinada attained 140 mm,

185 mm, and 205 mm at the end of 1st, 2nd and 3rd year respectively

(Murty, 1981). The values of VBGF obtained by him were L 60 = 219 mm, K =

0.83248 and to = -0.256198. N. japonicus along Kakinada coast had an

estimated total mortality (Z) of 1.86, fishing mortality (F) of 0.72, natural

mortality (M) of 1.14 and the exploitation rate (U) of 0.33 (Murty, 1983).

The estimated total annual stock was 1181 tons. The yield per recruit

(Y/R) curve showed that the Fishing mortality 'F' could be increased from

0.72 to 1.75. These fishes attained 185 mm, 255 mm, 285 mm on

completion of first, second and third year respectively (Murty, 1984), and

their growth parameters were L 0 = 314 mm, K = 0.75142, to = -0.173909

Year. The growth of males and females differed significantly in the case of

N. peronii from north west coast of Australia (Sainsbury and Whitelaw,

1984). Along the Madras coast N. japonicus had L,o of 305 mm, K =1.004, to

= 0.2257 Y, M = 2.5254 and F = 0.4599. The annual stock (2300 tons) and

standing crop (731 tons) were higher than the estimated landings which

suggested that increased effort can be put for increasing the total

27

production (Vivekanandan and James, 1986). The growth checks on the

scales of N. japonicus landed at Visakhapatnam were biannual, one during

January - March when feeding was poor and another during August -

October due to gonadal maturation and spawning (Rao and Rao, 1986b).

The maximum age of fish in the commercial landings estimated by them by

using the scales was three years.

Growth and mortality parameters observed for N. japonicus of

Kakinada trawl ground were, K = 0.52 per Year, L.= 339 mm, t4 = -0.16

Year, M = 1.11, F =1.53, Z = 2.64 (Murty, 1987a). The estimated length at

first capture (La) of the fish was 120 mm and he recommended for an

increased effort (F). The average recommended F for N. japonicus and N.

mesoprion along Kakinada was 1.95 and 2.7 respectively (Murty, 1987b).

Using two different methods John (1987) obtained values of L = 303 mm,

326 mm; K = 0.4 and to = 0.7 Year for N. japonicus along Kerala coast. At

an estimated value of Z = 1.37 per Year, the maximum sustainable yield

(MSY) of nemipterids above 80 mm along Kerala coast was 27000 t, slightly

higher than the catch level of the period. According to Devaraj and Gulati

(1988), N. japonicus from Mumbai region attained an average length of 150

mm, 250 mm and 280 mm in 1st, 2nd and 3rd year respectively. Their

estimated average annual yield of 6600 tons at F = 0.3504 for 1983-84 was

far less than the MSY level of 11,887 tons available from the inshore

28

waters. The average standing stock of N. japonicus along Gujarat was

419634 tons, Maharastra 64555 tons and Karnataka 38,621 tons. Along

Mangalore regions the estimated Lo was33 cm, K = 1.0 yr-1 , M=1.87 and Z =

5.65 with the E of 0.68. (Zacharia, 1998).

Along the Malaysian waters N. japonicus had Lco = 314 mm, K = 0.55

per Year, Z = 3.72, M =1.21, F = 2.51 (Isa, 1986). Along Bangladesh (Khan

and Mustafa, 1989), N. japonicus had 1..to = 20.14 cm and K =1.06 per Year

and the rate of exploitation was estimated to be 0.47. The N. mesoprion

landed at Visakhapatnam measuring 70-140 mm in length were found to

grow at the rate of 10 mm per month (Rao, 1989). The growth parameters

of N. japonicus for males and female was given by Samuel (1990) as Lco =

303, 265 mm; K = 0.542, 0.595; to = 0.19, 0.03 respectively. He also

observed that the males grew faster than females. Along the northern

Arabian Sea the stock parameters of N. japonicus were studied by Iqbal

(1991a), using length based stock assessment technique, ELEFAN. Three

species along east coast viz. N. mesoprion, N. tolu and N. delagoae had K

values of 1.080, 0.828 and 0.761 respectively and the corresponding Lo

Values were 207 mm, 282 mm and 271 mm respectively (Vivekanandan,

1991). Murty et al., (1992a) recorded increase of Threadfin landings from

22247 tons (1980-83) to 48100 tons (1984-88) with a maximum landing of

60000 tons during 1986.

29

Estimated growth parameters from length data of N. delagoae landed

at Tutukkudi were, Loc, = 362 mm and K = 1.0586 per year and t o =0.007

year (Hamsa et al., 1994). They also found that the average annual total

mortality coefficient Z for the species by trawl net was 3.29, with natural

mortality coefficient (M) 1.625. Yield per recruitment (Yr) indicated that the

fishing mortality (F = 1.665) was below Finax for age at first capture (to) of

0.4687 years. The recorded M/K ratio was 1.535. The estimated VBGF

parameters for N. japonicus of Bangladesh region using ELEFAN technique

were L.= 245 mm and K = 0.94; and the natural mortality coefficient M =

1.81 and F = 1.58 (Mustafa, 1994). Along the north west Coast of India N.

japonicus from Mumbai region grew to 193, 281 and 322mm at the end of

1 st, 2nd and 3rd year (Chakraborty, 1995). The VBGF parameters were L.=

356 mm, K = 0.75576, to = 0.03358254. The total, natural and fishing

mortality were respectively 3.58, 1.53 and 2.03, while the exploitation rate

and exploitation ratios were 0.54 and 0.56. Compared to the yield of 1645

tons during the study period under reference, estimated total stock and

standing stocks were 3047 tons and 810 tons respectively.

2.6. Distribution and fishery

The members of the family Nemipteridae are marine, distributed

along the Indo-Pacific regions. Most species of the genus Nemipterus

inhabit muddy and sandy bottom in coastal inshore as well as offshore

30

shelf waters, some in depths ranging upto 300 m. The species of

Parascolopsis occur in mud or sand bottom, but are mainly in deeper

waters upto a depth of 400 m. Species of Scolopsis and Scaevius inhabit

relatively shallow waters on muddy or sandy bottom closer to coral reefs.

Pentapodus are benthic, free swimming in regions closer to reefs. The

threadfin breams (Nemipterus spp.), whiptail breams (Pentapodus spp.),

monocle breams (Scolopsis spp.) and the dwarf monocle breams

(Parascolopsis. spp.), constitute multi species catch of the trawl gear. The

monocle breams and the dwarf monocle breams are of little importance in

fishery. The Scolopsis spp. is caught for aquarium trade, the Parascolopsis

spp. are occasionally caught by the fishermen along with other deep-water

resources. The whiptail breams are of artisan fisheries, occasionally taken

by recreational fisheries. Only the members of genus Nemipterus come in

the multi-species catch, often two or three species caught together.

2.6.1. Global distribution and the fishery

The distribution of the members of family Nemipteridae are limited to

tropical and sub tropical Indo-West Pacific region. There is no record of

their occurrence in Eastern Pacific. The report of their occurrence in

Atlantic was an error, and that at Mediterranean Sea is yet to be confirmed

(Russell, 1990a). The three genera: Nemipterus, Scolopsis and

Parascolopsis are widely distributed throughout the Indo- West Pacific

31

region. Whereas the genus Pentapodus is restricted to west Pacific. The

genus Scaevius is endemic to northern Australia. The landings of

nemipterids are not systematically reported, hence the landing statistics of

these fishes are inadequate. According to the catch statistics compiled by

FAO, the fishing area 71 lands the highest quantity followed by areas 61

and 57.

Zupanovic and Mohiuddin (1976) reported abundance of N. japonicus

along the northeastern Arabian Sea in the 50-125 m depth zone.

Nemipterids formed 5.3% of demersal community in the Malaysian shallow

waters (Chan and Liew 1986). In the Malaysian EEZ, nemipterid species

formed one of the important by-catch (Mohamed 1986). In another study

9.7% of the overall catch of demersal survey yielded threadfins constituting

eight species, (Said et al., 1986) of which N. nemurus was most abundant.

This group was second in abundance after Lutjanidae (Mohamed et al.,

1986). Along South China Sea, the Nemipterids formed the third largest

commercially important resource (Mohsin et al., 1987). Threadfins formed

a small resource along Arabian Gulf (El-Sedfy et al., 1987). Along Pakistan

waters, N. metopias formed one of the important constituents of trawl catch

during the northeast monsoon period (Iqbal, 1991b).

32

2.6.2 Distribution and Fishery along the Indian Coast

Nemipterids were identified for the first time in India by Day (1878)

who also recorded their distribution. Banse (1959) observed that, off

Kochi, N. japonicus were available when the oxygen content was above 0.25

to 0.50 In1L-1 N. japonicus were first reported from the southern coast

(Anon, 1960) and later along Mangalore coast (Kuthalingam, 1965).

Krishnamoorthi (1973) observed that the peak abundance of N. japonicus

along Andhra coast was from January to April coinciding with the

upwelling period. Silas et al. (1976) reported existence of the rich

nemipterid resource on the continental shelf beyond 50 m depth, especially

in the 75-100 m belt, often-forming 75% of the trawl catches along different

parts of the Indian coast. Along Kakinada, they were found to form about

9.7% of total trawl catch (Muthu et al., 1977). Murty (1984) recorded that

50% of nemipterid landings at Kakinada was constituted by N. japonicus,

followed by N. mesoprion, N. tolu, and N. luteus. N. japonicus are found all

along the Indian coast including Andaman waters. Nemipterids was one of

the important resources available for exploitation during the 1980's

(Joseph, 1986). At Sassoon Dock, Mumbai, which is one of the major

landing centers of northwest coast, the landing of threadfins started during

1970's (Pillai, 1986). These were projected as one of the important

resources from the deep-water region (Sudarsan et al., 1988). N. japonicus

33

and N. mesoprion were the two dominant species representing the threadfin

breams in the trawl catch in the region. Dwarf monocle bream

(Parascolopsis) was also caught with the threadfin breams in the deeper

waters in small quantity. Vivekanandan (1990) reported that N. japonicus

were dominant in shallow waters while N. mesoprion (N. randalli?) was

dominant in the deeper waters. Reuben et al., (1989), while assessing the

demersal resource between 1961- 1985, along northeast coast of India

observed that threadfin breams were under exploited in the region. Nair

and Jayaprakash (1986) observed that N. mesoprion and N. japonicus were

dominant in the catch from 35-40 m depth off Kochi during monsoon.

Kasim et al., (1988), based on the landing figures reported that threadfin

breams formed 50% of the perch resources. In the trawling grounds at 10-

80 m depth between Lat.17° and 18° N. along the east coast of India the

nemipterids formed about 14.7% of the catch (Shastry and Chandrasekhar,

1986). Landing along Waltair comprised of N. mesoprion measuring 70 to

140 mm (Rao, 1989). Along the Karnataka coast, major part of demersal

resource consisted of threadfin breams (Biradar, 1987). Murty et al. (1992)

observed that N. japonicus and N. mesoprion formed two important species

in the fishery along Kerala State. Sudarsan (1993) opined that

quantitatively nemipterids were one of the most important marine

resources of India. The results of survey conducted on board FORV Sagar

34

Sampada (Kunjipalu, 1990; Nair and Reghu, 1990; Nair et al., 1996;

Sivakami, 1990; Panicker et al., 1993; Bensam et al., 1996, and Menon et

al., 1996) also revealed the abundance of Nemipterids in the deep waters

along our coast, especially in the southwest sector.